KR20080033665A - Led having vertical structure and method of making the same - Google Patents

Abstract

An LED having a vertical structure and a method of manufacturing the same are provided to omit an etching process by using a conductive layer of an n-type semiconductor thin film layer, thereby reducing manufacturing costs. An active layer(2) having a quantum well structure is located in between an n-type nitride gallium layer(1) as an electron injection layer and a p-type nitride gallium layer(3) as a hole injection layer. The n-type nitride gallium layer is exposed by etching the p-type nitride gallium layer and the active layer. An n-type electrode(6) is formed at the exposed n-type nitride gallium layer. A p-type electrode(7) is formed on the p-type nitride gallium layer. A buffer layer(5) is formed between a substrate(4) and the n-type nitride gallium layer.

Description

Vertical light emitting device and its manufacturing method {LED having vertical structure and method of making the same}

1 is a cross-sectional view showing an example of a general light emitting device.

2 to 4 are cross-sectional views showing an embodiment of the manufacturing method of the present invention,

2 is a cross-sectional view illustrating a step of forming a conductive layer on a substrate.

3 is a cross-sectional view illustrating a step of forming a semiconductor layer on a conductive layer.

4 is a cross-sectional view showing a step of forming a support layer.

5 is a cross-sectional view showing an embodiment of a vertical light emitting device of the present invention.

<Brief description of the main parts of the drawing>

100: substrate 101: package body

110: through hole 120: mounting portion

200 electrode 210 front electrode

220: rear electrode 300: partition wall

310: filler 400: light emitting device

The present invention relates to a vertical light emitting device and a method of manufacturing the same, and more particularly, to a vertical light emitting device that can improve the luminous efficiency and reliability of the light emitting device.

Light Emitting Diodes (LEDs) are well-known semiconductor light emitting devices that convert current into light.In 1962, red LEDs using GaAsP compound semiconductors were commercialized, along with GaP: N series green LEDs. It has been used as a light source for display images of electronic devices, including.

The wavelength of light emitted by such LEDs depends on the semiconductor material used to make the LEDs. This is because the wavelength of the emitted light depends on the band-gap of the semiconductor material, which represents the energy difference between the valence band electrons and the conduction band electrons.

Gallium nitride compound semiconductors (Gallium Nitride: GaN) have high thermal stability and wide bandgap (0.8 to 6.2 eV), which has attracted much attention in the development of high-power electronic components including LEDs.

One reason for this is that GaN can be combined with other elements (indium (In), aluminum (Al), etc.) to produce semiconductor layers that emit green, blue and white light.

In this way, the emission wavelength can be adjusted to match the material's characteristics to specific device characteristics. For example, GaN can be used to create white LEDs that can replace incandescent and blue LEDs that are beneficial for optical recording.

Due to the advantages of these GaN-based materials, the GaN-based LED market is growing rapidly. Therefore, since commercial introduction in 1994, GaN-based optoelectronic device technology has rapidly developed.

The brightness or output of the LED using the GaN-based material as described above is large, the structure of the active layer, the light extraction efficiency to extract light to the outside, the size of the LED chip, the type and angle of the mold (mold) when assembling the lamp package , Fluorescent material and the like.

On the other hand, one of the reasons why the growth of GaN-based semiconductors is more difficult than other III-V compound semiconductors is that there are no high-quality substrates, that is, wafers made of materials such as GaN, InN, and AlN.

Therefore, the LED structure is grown on a heterogeneous substrate such as sapphire, and many defects are generated, and these defects have a great influence on the LED performance.

As shown in FIG. 1, the basic structure of the LED of GaN-based material is a quantum well structure between an n-type gallium nitride layer 1 as an electron injection layer and a p-type gallium nitride layer 3 as a hole injection layer. An active layer 2 having a quantum well is located.

At this time, one side of the p-type gallium nitride layer 3 and the active layer 2 is etched so that the n-type gallium nitride layer 1 is exposed, the n-type gallium nitride layer (1) is exposed to the etching An n-type electrode 6 is formed, and a p-type electrode 7 is formed in the p-type gallium nitride layer 3.

Such a structure is formed on the substrate 4, in which a buffer layer 5 is usually formed first between the substrate 4 and the n-type gallium nitride layer 1, which is an undoped GaN layer.

This is to obtain a high quality n-type gallium nitride layer (1). That is, a high quality n-type gallium nitride layer 1 is required to realize a high-performance optical device, and when the n-type gallium nitride layer 1 containing a dopant is formed directly on the substrate 4, its crystallinity is increased. The problem of this inherently thin film can be greatly reduced.

As described above, when the nitride semiconductor thin film is grown on the dissimilar substrate 4, crystal defects due to the crystal lattice mismatch between the heterogeneous substrate 4 and the nitride semiconductor thin film are formed near the interface.

Among these crystal defects, threading dislocation in particular penetrates into the thin film and propagates through the active layer 2 of the light emitting element to the surface. Therefore, in order to manufacture a high performance device, it is required to grow a high quality nitride thin film having a low crystal defect density.

A general method of preparing a high quality nitride semiconductor thin film on the hetero substrate 4 is as follows. First, the buffer layer 5 is grown on the substrate 4. The growth of the buffer layer 50 forms a thin nitride semiconductor nucleation layer at low temperature, and then increases the growth temperature to a high temperature of 1000 ° C. or more to form an island shape. A high temperature nitride thin film layer is grown on the nucleation layer.

In this case, in order to grow a high-definition thin film of low crystal defects, the thin film growth starts on the island-shaped initial nuclei, and the degree of lateral growth is important at the same time as the vertical growth.

Later, as the thin film growth continues, the initial islands encounter each other by lateral growth and mix with each other. At this time, the pinholes are deeply formed in the portions where the islands meet laterally. These pinholes gradually fill up as the thin film growth continues in the vertical direction and the horizontal growth continues, and the thin film surface eventually becomes flat to form the buffer layer 5.

As such, high-quality nitride semiconductors grown on heterogeneous substrates start with an initial seed in the form of islands and undergo an evolutionary process that is laterally mixed and flattened. At this time, the evolution from flat to thin film is highly dependent on the lateral growth rate of the film.

However, when silicon is implanted with an n-type dopant during nitride semiconductor thin film growth, the silicon changes the surface chemistry at the thin film growth surface, thereby decreasing the mobility of the major elements of thin film growth on the surface, thereby decreasing the lateral growth rate of the thin film. Let's do it. As a result, the planarization of the thin film is delayed and the quality of the crystal is also degraded.

Therefore, as described above, in general, in order to grow the high quality n-type gallium nitride layer 1, a high quality undoped nitride semiconductor thin film is first grown on the dissimilar substrate 4 to form the buffer layer 5. After that, an n-type gallium nitride layer 1 is grown thereon.

The buffer layer 5 is an undoped nitride semiconductor thin film, which is a high quality thin film having low crystal defects but has a very low electrical conductivity.

Therefore, in order to manufacture a conventional vertical light emitting device using a nitride semiconductor thin film formed on the heterogeneous substrate 4, the buffer layer 5 having a very low electrical conductivity exposed after removing the sapphire substrate 4 is removed using an etching process. Should be.

This etching process is to expose a high-quality n-type gallium nitride layer (1) having excellent electrical conductivity, and to form an n-type electrode thereon to implement a high-performance vertical light emitting device.

However, in the case of the vertical light emitting device, it is very difficult to separate the thin film layer from the substrate and then use the etching equipment to etch the separated devices, which causes additional costs and lowers the production yield.

An object of the present invention is to provide a vertical light emitting device having a high quality n-type gallium nitride thin film layer having excellent electrical conductivity and excellent crystallinity as a thin film layer initially formed on a dissimilar substrate, and a method of manufacturing the same.

As a first aspect for achieving the above technical problem, the present invention, forming a conductive layer including a nitride layer and a nitride semiconductor layer containing Si on the substrate; Forming a plurality of semiconductor layers on the conductive layer; Forming a first electrode on the semiconductor layer; Removing the substrate; It is preferably configured to include a second electrode on the conductive layer.

The conductive layer may include a plurality of nitride layers including the Si and a nitride semiconductor layer, and may be alternately formed.

The nitride layer including Si may include Si and In, and more preferably, a SiInN layer.

In addition, the nitride semiconductor layer may be an Al _x In _y Ga _1-xy N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1) layers.

Meanwhile, after the forming of the first electrode, the method may further include forming a support layer made of a metal or a conductive semiconductor.

The forming of the conductive layer may be performed by increasing the temperature during growth of the conductive layer. That is, it can be formed by starting to grow at a low temperature, rising to a high temperature in the middle.

The nitride layer including Si may have an atomic layer thickness of several mono layers, and the nitride semiconductor layer may have a thickness of 1 to 50 nm.

As a second aspect for achieving the above technical problem, the present invention, forming a conductive buffer layer including a semiconductor layer and a nitride semiconductor layer, at least one dopant is bonded to the substrate; Forming a plurality of semiconductor layers on the conductive buffer layer; Forming a first electrode on the semiconductor layer; Removing the substrate; It is preferably configured to include a second electrode on the conductive buffer layer.

As a third aspect for achieving the above technical problem, the present invention, the support layer; A first electrode on the support layer; A plurality of semiconductor layers on the first electrode; A conductive layer disposed on the plurality of semiconductor layers, the nitride layer including Si and a nitride semiconductor layer; It is preferably configured to include a second electrode located on the conductive layer.

In this case, the first electrode may be formed of two layers of an ohmic electrode and a reflective electrode, or may be a reflective electrode having ohmic characteristics.

The plurality of semiconductor layers may further include a first conductive semiconductor layer; A light emitting layer on the first conductive semiconductor layer; It may be configured to include a second conductive semiconductor layer located on the light emitting layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

While the invention allows for various modifications and variations, specific embodiments thereof are illustrated by way of example in the drawings and will be described in detail below. However, it is not intended to be exhaustive or to limit the invention to the precise forms disclosed, but rather the invention includes all modifications, equivalents, and alternatives consistent with the spirit of the invention as defined by the claims.

Like reference numerals denote like elements throughout the description of the drawings. In the drawings the dimensions of layers and regions are exaggerated for clarity. In addition, each embodiment described herein includes an embodiment of a complementary conductivity type.

When an element such as a layer, region or substrate is referred to as being on another component "on", it will be understood that it may be directly on another element or there may be an intermediate element in between. . If a part of a component, such as a surface, is expressed as 'inner', it will be understood that this means that it is farther from the outside of the device than other parts of the element.

Furthermore, relative terms such as "beneath" or "overlies" refer to the relationship of one layer or region to one layer or region and another layer or region with respect to the substrate or reference layer, as shown in the figures. Can be used to describe.

It will be understood that these terms are intended to include other directions of the device in addition to the direction depicted in the figures. Finally, the term 'directly' means that there is no element in between. As used herein, the term 'and / or' includes any and all combinations of one or more of the recorded related items.

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers, and / or regions, such elements, components, regions, layers, and / or regions It will be understood that it should not be limited by these terms.

These terms are only used to distinguish one element, component, region, layer or region from another region, layer or region. Thus, the first region, layer or region discussed below may be referred to as the second region, layer or region.

Embodiments of the present invention will be described with reference to a gallium nitride (GaN) based light emitting device (LED) formed on a nonconductive substrate such as, for example, a sapphire (Al ₂ O ₃ ) based substrate. However, the present invention is not limited to this structure.

Embodiments of the invention may use other substrates, including conductive substrates. Thus, combinations of AlGaInP diodes on GaP substrates, GaN diodes on SiC substrates, SiC diodes on SiC substrates, SiC diodes on sapphire substrates, and / or GaN, SiC, AlN, ZnO and / or nitride based diodes on other substrates may be included. have. Moreover, the present invention is not limited to the use of the diode region. Other forms of active area may also be used in accordance with some embodiments of the present invention.

As shown in FIG. 2, a substrate 10 is prepared, and a semiconductor layer to which an n-type dopant is bonded is formed on the substrate 10. Such n-type dopant may be conventionally used silicon (Si). Therefore, the semiconductor layer to which the n-type dopant is bonded may be a nitride layer including Si.

As an example of such a semiconductor layer, a silicon indium (In) source and an indium (In) source, which may be used as an n-type dopant of a nitride semiconductor, are supplied for a predetermined time to form a silicon indium nitride (SiInN) layer 21.

When forming the SiInN layer 21 as described above, it is preferable to use hydrogen or nitrogen as the carrier gas flowing in the growth equipment, and use ammonia as the Group 5 source.

In addition, the SiInN layer 21 preferably has a monolayer atomic layer thickness. Herein, the monolayer atomic layer thickness means a thickness formed by combining Si and N in a thin film growth direction, or a thickness formed by In and N combining in a thin film growth direction, and may generally have a thickness of several to several tens of mono layers. have.

As described above, when the SiInN layer 21 is formed to a thin thickness, the nitride semiconductor layer 22 can be formed thereon. In this case, the nitride semiconductor layer 22 may be formed while maintaining the crystallinity of the substrate 10.

Next, a nitride semiconductor layer (Al _x In _y Ga _1-xy N: 0 ≦ x, y ≦ 1: 22) having a predetermined thickness is formed on the SiInN layer 21. Here, x and y represent the contents of Al and In, which are Group V elements, and x and y each have a value between 0 and 1, and the sum does not exceed 1 (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and thus, the Ga content may vary.

The nitride semiconductor layer 22 preferably has a thickness of 1 to 50 nm.

Thereafter, the SiInN layer 21 is formed as described above, and the nitride semiconductor layer 22 is formed. The process of growing the initial SiInN layer 21 and the nitride semiconductor layer 22 can be grown at a relatively low temperature, it can be grown at a temperature of approximately 500 to 600 ℃.

When the thickness of the thin film layer formed through this repetition process is about 10 to 200 nm, the growth temperature is increased to a high temperature of 1000 ° C. or higher, and the SiInN layer 21 and the nitride semiconductor layer 22 are alternately formed repeatedly.

In the case of the conventional horizontal nitride semiconductor light emitting device, the low temperature buffer layer should have an insulating property. This is because when the low temperature buffer layer is electrically conductive, it may cause leakage current of the device, which may degrade device performance.

However, in the case of the nitride semiconductor vertical light emitting device, it is preferable that the low temperature buffer layer has high electrical conductivity, and the conductive layer 20 according to the present invention can act as a conductive buffer layer, that is, a conductive buffer layer, and the SiInN layer ( 21) has a feature of having high electrical conductivity by silicon (Si) which is efficiently supplied from.

Indium (In) of the SiInN layer 21 according to the present invention has a high volatility, and has inherent characteristics of having a larger atomic radius than other atoms and a relatively weak bonding force with nitrogen. Therefore, upon forming the nitride semiconductor layer 22 on the SiInN layer 21, indium (In) may increase the surface mobility of other atoms on the thin film growth surface, thereby facilitating the formation of a high quality nitride semiconductor thin film. Can be.

As a result, Si acts as a dopant to form a conductive layer 20 having electrical conductivity as a whole.

As described above, the SiInN layer 21 and the nitride semiconductor layer 22 are repeatedly formed at a high temperature of 1000 ° C. or higher so that the total thickness of the thin film formed on the substrate 10 reaches 0.1 to 4 μm.

Thereafter, as shown in FIG. 3, a plurality of nitride based semiconductor layers 30 are formed. The nitride semiconductor layer 30 is composed of an n-type semiconductor layer 31 as an electron injection layer, a light emitting layer 32, and a p-type semiconductor layer 33 as a hole injection layer, in which light is generated. The light emitting layer 32 has a single or multiple quantum well structure (QW) of a nitride semiconductor.

The n-type semiconductor layer 31 and the p-type semiconductor layer 33 may have a different stacking order. That is, the p-type semiconductor layer 33 may be formed first, and the light emitting layer 32 and the n-type semiconductor layer 31 may be formed on the p-type semiconductor layer 33.

As the n-type semiconductor layer 31 and the p-type semiconductor layer 33, an electrically conductive nitride-based semiconductor layer may be used.

As described above, according to the present invention, the conductive layer 20 formed by the repeated lamination of the SiInN layer 21 and the nitride semiconductor layer 22 has high quality n-type electrical conductivity. This is because the SiInN layer 21 can efficiently supply silicon, which is an n-type dopant, through the thermal diffusion process into the nitride semiconductor layer 22.

On the semiconductor layer 30 formed as described above, as shown in FIG. 4, the first electrode 40 is formed.

The first electrode 40 may be formed of a transparent ohmic electrode 41 and a reflective electrode 42. The transparent ohmic electrode 41 may be formed of a transparent conductive oxide such as indium tin oxide (ITO) and may improve ohmic characteristics.

In addition, the reflective electrode 42 allows the light generated in the light emitting layer 32 of the semiconductor layer 30 to be reflected, and is made of silver (Ag), nickel (Ni), or aluminum (Al), and these It may be made of an alloy.

In some cases, the first electrode 40 may be formed of a reflective electrode having ohmic characteristics. In this case, the first electrode 40 may also include silver (Ag), nickel (Ni), or aluminum ( Al), and alloys thereof.

Thereafter, the support layer 50 may be formed on the first electrode 40. The support layer 50 preferably uses a metal or a conductive semiconductor having excellent heat dissipation characteristics.

Thereafter, the substrate 10 is removed by physical or chemical etching, or by laser, and the surface of the conductive layer 20 exposed by the removal of the substrate 10 is treated by chemical etching. To control.

The control of the surface shape can improve the light extraction efficiency by controlling the surface shape of the conductive layer 20 and at the same time can improve the metal ohmic characteristics by increasing the surface area.

After such a process, as shown in FIG. 5, the n-type electrode pad 61 is formed on the conductive layer 20, and the p-type electrode pad 62 may also be formed on the support layer 50. ) May be formed.

As described above, when the light emitting device structure is formed on the conductive layer 20, a high performance nitride semiconductor vertical light emitting device having a low production cost and a high yield may be realized.

Typical side or horizontal light emitting devices implement a high performance device having high quality crystallinity by continuously growing a light emitting layer and a p-type nitride semiconductor layer on an n-type nitride semiconductor layer.

However, in the case of the vertical light emitting device, since the n-type electrode pad should be formed on the exposed surface after removing the heterogeneous substrate, the exposed semiconductor layer thin film should be a high quality n-type nitride semiconductor thin film having excellent electrical conductivity.

Therefore, the undoped nitride thin film layer on the substrate formed in a conventional conventional procedure should be removed. That is, the conventional method of manufacturing a vertical light emitting device using a nitride semiconductor thin film formed on a heterogeneous substrate includes removing the first thin film layer having low electrical conductivity formed on the heterogeneous substrate by using an etching process.

However, according to the present invention, by forming a thin film layer having excellent electrical conductivity and excellent crystallinity as the first thin film layer on a heterogeneous substrate, a high performance vertical light emitting device can be manufactured without requiring an etching process after removing the substrate.

Therefore, when the vertical light emitting device is implemented by using the conductive layer 20 of the high quality n-type semiconductor thin film layer according to the present invention, the production cost of the device can be greatly lowered since the etching process of high difficulty is not required, Process defects generated in the process can be reduced, and the production yield of the light emitting device can be increased. In addition, by using a high quality n-type thin film, the reliability of the light emitting device can be greatly improved.

The above embodiment is an example for explaining the technical idea of the present invention in detail, and the present invention is not limited to the above embodiment, various modifications are possible, and various embodiments of the technical idea are all protected by the present invention. It belongs to the scope.

The present invention as described above has the following effects.

First, it is possible to eliminate the high-level etching process required in manufacturing a conventional vertical light emitting device.

Second, the manufacturing cost of the vertical light emitting device using the nitride semiconductor thin film layer grown on the dissimilar substrate can be reduced, and the production yield can be improved.

Third, it is possible to improve the performance and reliability of the vertical light emitting device by providing a conductive layer having high quality crystallinity and electrical conductivity.

Claims (16)

Forming a conductive layer including a nitride layer including Si and a nitride semiconductor layer on the substrate; Forming a plurality of semiconductor layers on the conductive layer; Forming a first electrode on the semiconductor layer; Removing the substrate; Forming a second electrode on the conductive layer, characterized in that it comprises a method of manufacturing a vertical light emitting device. The method of claim 1, wherein the conductive layer is formed by alternately forming a nitride layer and a nitride semiconductor layer including two or more Si. The method of manufacturing a vertical type light emitting device according to claim 1, wherein the nitride layer containing Si contains In. The method of manufacturing a vertical light emitting device according to claim 1, wherein the nitride layer containing Si is a SiInN layer. 2. The vertical layer of claim 1, wherein the nitride semiconductor layer is an Al _x In _y Ga _1-xy N layer, wherein 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1 layers. Method of manufacturing a light emitting device. The method of claim 1, further comprising, after forming the first electrode, forming a support layer formed of a metal or a conductive semiconductor. The method of manufacturing a vertical type light emitting device according to claim 1, wherein the nitride layer containing Si has a monolayer atomic layer thickness. The method of claim 1, wherein the nitride semiconductor layer has a thickness of 1 to 50nm. The method of claim 1, wherein the forming of the conductive layer comprises increasing the temperature during growth of the conductive layer. Forming a conductive buffer layer on the substrate, the conductive buffer layer comprising a nitride semiconductor layer and a semiconductor layer having at least one dopant bonded thereto; Forming a plurality of semiconductor layers on the conductive buffer layer; Forming a first electrode on the semiconductor layer; Removing the substrate; And forming a second electrode on the conductive buffer layer. A support layer; A first electrode on the support layer; A plurality of semiconductor layers on the first electrode; A conductive layer disposed on the plurality of semiconductor layers, the nitride layer including Si and a nitride semiconductor layer; And a second electrode positioned on the conductive layer. 12. The vertical light emitting device of claim 11, wherein the first electrode is an ohmic electrode, a reflective electrode, or a reflective electrode having ohmic characteristics. 12. The vertical light emitting device of claim 11, wherein the conductive layer is formed by alternately forming a nitride layer including the Si and a nitride semiconductor layer. The vertical type light emitting device according to claim 13, wherein the nitride layer containing Si is a SiInN layer. The method of claim 11, wherein the plurality of semiconductor layers, A first conductive semiconductor layer; A light emitting layer on the first conductive semiconductor layer; And a second conductive semiconductor layer positioned on the light emitting layer. 12. The vertical light emitting device according to claim 11, wherein the nitride layer containing Si has a monolayer atomic layer thickness and the nitride semiconductor layer has a thickness of 1 to 50 nm.

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